Information on Samlex Desktop Switching Power Supplies

Back to Home Information on

Desktop and Rackmount
Switching Power Supplies
and Battery Chargers
Compiled and Formerly Maintained by Robert Meister WA1MIK (SK)
Currently Maintained by Mike Morris WA6ILQ.

Click here or the icon above for the Samlex America web page.

Recently multiple people have reported that Samlex no longer "supports field repair" nor do they "disclose schematics".
Samlex manuals are readily available online but many do not contain a schematic diagram.
This is NOT the way to encourage people to purchase your product.
Your page maintainer has about a dozen of the SEC-100BRM power supplies and a similar number of the SEC-1250UL and SEC-1230UL battery chargers spread across a number of commercial radio sites.
If I can't get a schematic when I need it I'll be looking for a new manufacturer.
Samlex makes GOOD stuff, I'd hate to have to switch.

Does anyone have a reverse engineered / hand drawn schematic of the SEC-1230UL or SEC-1250UL chargers?
Or the SEC-2012MPSB power supply module? (or any other Samlex units?) Anonymous donations are fine...

Manuals and Useful Information:

SEC-1212 and SEC-1223 Power Supply Manual 2.0 MB PDF file by Samlex
Even though the model number indicates 12A, the SEC-1212 supply is only rated for 10 amps continuous. It relies on convection cooling and has no fan. Because there's no fan, the SEC-1212 illuminated power switch is in the lower right corner of the front panel. Click here for an inside photo (courtesy of Bob WA1MIK).
The SEC-1223 is rated for 23 amps continuous (the only one whose model number and current capability agree) and it has a thermostatically-controlled cooling fan. Since there's a fan inside, the SEC-1223 illuminated power switch is in the lower left corner of the front panel. Click here for an inside photo (courtesy of Bob WA1MIK).
The DC output terminals on both of these models are further apart and more centrally located on the rear panel than they are on the SEC-1235 supply. There is room on the front panel of either unit to add Anderson PowerPoles.

SEC-1223 Schematic and Parts List 530 KB PDF file redrawn by Tom NØSS
The SEC-1212 and SEC-1235 supplies are similar as are a Kenwood KPS-15 and a Yaesu FP-1023.

SEC-1223BBM Power Supply with Battery Backup Manual 1.7 MB PDF file by Samlex
The same as an SEC-1223 but has an extra pair of terminals to attach to a battery. Provides up to 4A of charging current.

SEC-1235 and SEC-1235M Power Supply Manual 1.6 MB PDF file by Samlex
These supplies are rated for 30A continuous and have a thermostatically-controlled cooling fan. The SEC-1235M has analog voltage and current meters on the front panel and is their only desktop model that has meters. Because of the possibility of meters, the illuminated power switch is on the front right corner above the internal cooling fan. Click here for an inside photo of an SEC-1235M (courtesy of Phil AD5X).
The DC output terminals are closer together and closer to the side of the unit than they are on the SEC-1212 or SEC-1223 supplies.

SEC-12xxP Power Supply Manual 1.3 MB PDF file by Samlex
The SEC-12xxP models are newer versions of the SEC-12xx supplies. They have the same ratings as the SEC-12xx supplies however they will automatically handle 120 or 240VAC input power; no internal jumper change required. The SEC-1235PM has a dual back-lit meter and an illumination on/off switch. The fan, for those supplies that have one, has been relocated to the rear panel of the supply. This manual actually covers all of the SEC-12xxP series switching power supplies.

Samlex desktop switching power supplies have two adjustment pots inside. The one that is closest to the rear of the chassis is labeled VR2 and it adjusts the output voltage. The one that is more centrally located and easier to get to is labeled VR1 and it sets the maximum output current. Most desktop switching power supplies do not have an over-voltage crowbar circuit and neither do the Samlex units, therefore the output voltage can easily be adjusted to 12-16VDC.

Samlex desktop switching power supplies will go into current limiting a few amps above their rated maximum current. When this occurs, the voltage drops down to just a couple of volts but the current remains at the maximum value; it does not fold back as happens in Astron and most other linear power supplies.

A number of the Samlex desktop switching power supplies use odd DC output terminals that fit into 1/2 inch square holes in the rear of the chassis. They accept 5mm round terminal pins. Stranded wires should be twisted and tinned to become a solid wire or crimped into an appropriate terminal pin. They use a 5/64 hex socket set screw that is #10, 24 TPI, 5/16 inch long. A hex key (Allen wrench) is supplied with the power supply. Older supplies used a slotted brass set screw that was easily broken. An M4x0.7 screw also fits.

Samlex desktop switching power supplies produced for 120VAC mains voltage have an internal line fuse with the following ratings:
SEC-1212: 5mm x 20mm Glass Fuse, 250V, 3.0A, Time Delay Type, LittelFuse 239003
SEC-1223: 5mm x 20mm Glass Fuse, 250V, 6.3A, Time Delay Type, LittelFuse 21806.3
SEC-1235: 5mm x 20mm Glass Fuse, 250V, 8.0A, Time Delay Type, LittelFuse 218008
When purchasing these fuses, they often have a "TnA" part number, where "T" stands for "Time Delay" (also known as Slo-Blo) and "n" is the current in amps. See the manual for 240VAC mains fuse ratings.

Eric Lemmon WB6FLY (SK) performed load tests of the Samlex SEC-1212 and the Yaesu FP-1023 (a Samlex SEC-1223 inside) that can be found in the "AC and DC Power-Related Information" section of the Technical Information page of this website.

There is about an inch of room behind the front panel to install a small LED or LCD meter and selector switch, but the metal is pretty thick and it may not be easy to cut a square hole to insert the meter through. See the inside photos above. It might be easier to install an external voltmeter and ammeter, or just buy a supply with meters, such as the SEC-1235M.

Samlex offers a rack mount chassis to hold their desktop switching power supplies. See their web page for further details and models.

Modifications and Datasheets:

SEC-100BRM 13.8 volt 100 amp Rack-Mount Power Supply 910 kB PDF file
SEC-100BRM 13.8 volt 100 amp Rack-Mount Power Supply Specification Sheet 327 kB PDF file
This is the manual for the above 40, 60, 80, and 100 amp rack mount power supplies. Internally they use from two to five 20-amp modules that are in parallel (marketed as "N+1 redundancy"). A lower amperage unit can be field upgraded by field installing additional SEC-2012MPSB modules (at the time of this update they were about US$80 to $100 each). This unit has a front panel voltmeter / ammeter, a fan failure LED, and five green LEDs showing the functionality of the internal 20-amp SEC-2012MPSB modules (from two to five) that are in parallel (marketed as "N+1 redundancy").
There is a 25 pin D-sub female connector on the rear for remote monitoring of the DC voltage output, the DC current drawn, the output of each of the five 20-amp modules, failure of either of the two DC fans, the presence of AC mains power, and more.
The pinout of that connector is here (it's just one page from the manual). There is no single output that indicates a module failure but you can create one by diode-ORing the individual module fail pins..
Note that this model is NOT modifiable for 240 volt AC input, Samlex makes the SEC-100BRM-230 model for that. They also make other models with 24 volt output.
Your page maintainer has about a dozen of the 12 volt 100 amp supplies in commercial mountaintop service, one site has five supplies.
I've always ordered a 100 amp unit, the last few times I've received a 40 amp unit (two modules) and the other three modules in their own wrapping (I've had to assemble them).
There are four high current connections on the rear, two for the DC output and two for a backup battery. The two ground terminals are paralleled inside. Internally there is a battery charger feature that can be easily disabled if the site backup battery has its own charger... however it is NOT a multistage charger, it is a simple constant-voltage trickle charger (8 amps maximum of charging current) using a 0.39 ohm power resistor (actually two 0.78 ohm resistors in parallel) between the power supply positive output terminal and the battery positive terminal. Depending on the output voltage of the supply and the type of battery it could overcharge or undercharge your battery, and in case of a extended power failure the 8 amp (maximum) trickle charger could take a very, very, very long time to recharge your site battery. Your page maintainer uses the SEC-series power supplies with the internal charger disabled. The battery charging function at our sites is provided by one or two of the SEC-1250UL (50 amps) or SEC-1235UL (35 amps) battery chargers - each site has between 400 and 800 amp-hours of backup battery.

SEC-1230UL 13.8 volt 30 amp Multistage battery Charger Spec Sheet 481 KB PDF file
This is the specification sheet for the yellow Samlex 30 amp multistage battery charger.

SEC-1215UL (15 amp) and SEC-1230UL (30 amp) 13.8 volt Multistage battery Charger Manual 2.2 MB PDF file
This is the manual for the yellow Samlex 15 and 30 amp multistage battery chargers.
Your page maintainer has a few of the 30 amp units at mountaintop sites.

SEC-1250UL 13.8 volt 50 amp Multistage battery Charger Spec Sheet 447 KB PDF file
This is the specification sheet for the yellow Samlex 50 amp multistage battery chargers.

SEC-1250UL 13.8 volt 50 amp Multistage battery Charger Manual 2.3 MB PDF file
This is the manual for the yellow Samlex 50 amp multistage battery chargers.
Your page maintainer has a number of these 50 amp units at mountaintop sites.
One trick tp tell them apart: The 30 amp charger has one meter, the 50 amp model has two.

SEC-1223 120V to 240V Modification 750 kB PDF file
The other supplies can be similarly modified; the procedure is described in the manuals above. The yellow jumper wire can easily be seen in the two photos above, between the two large filter capacitors.
The newest SEC-12xxP models automatically detect and handle either 120V or 240V input voltages, so no jumper is present in these units.

SEC-1223 RF Filter Modification 720 KB PDF file by Nigel ZL2DF

KA7500B Switching Mode Regulator IC Datasheet 61 KB PDF file
Many Samlex desktop switching power supplies use this IC.

TL494 Switching Mode Regulator IC Datasheet 1.3 MB PDF file
This is functionally equivalent to the KA7500B above and is a very common IC in desktop switching power supplies made by Astron and other companies.

Samlex SEC-1223 Modifications 1.8 MB PDF file
While listed for the SEC-1223, this also pertains to the SEC-1212, SEC-1235, and SEC-1235M power supplies. The yellow 120V/240V jumper is similar in the other models but the pins are labeled with different letters. It also contains an unofficial schematic and parts list. Some of this information is available separately above.

Samlex SEC-1223 Power Supply Repair 1.0 MB PDF file
A repair article by Paul Robertson N2XZF.

Back to the top of the page
Back to Home

This page initially created 01-Jul-2020.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.

	SEC-1212 and SEC-1223 Power Supply Manual 2.0 MB PDF file by Samlex Even though the model number indicates 12A, the SEC-1212 supply is only rated for 10 amps continuous. It relies on convection cooling and has no fan. Because there's no fan, the SEC-1212 illuminated power switch is in the lower right corner of the front panel. Click here for an inside photo (courtesy of Bob WA1MIK). The SEC-1223 is rated for 23 amps continuous (the only one whose model number and current capability agree) and it has a thermostatically-controlled cooling fan. Since there's a fan inside, the SEC-1223 illuminated power switch is in the lower left corner of the front panel. Click here for an inside photo (courtesy of Bob WA1MIK). The DC output terminals on both of these models are further apart and more centrally located on the rear panel than they are on the SEC-1235 supply. There is room on the front panel of either unit to add Anderson PowerPoles.
	SEC-1223 Schematic and Parts List 530 KB PDF file redrawn by Tom NØSS The SEC-1212 and SEC-1235 supplies are similar as are a Kenwood KPS-15 and a Yaesu FP-1023.
	SEC-1223BBM Power Supply with Battery Backup Manual 1.7 MB PDF file by Samlex The same as an SEC-1223 but has an extra pair of terminals to attach to a battery. Provides up to 4A of charging current.
	SEC-1235 and SEC-1235M Power Supply Manual 1.6 MB PDF file by Samlex These supplies are rated for 30A continuous and have a thermostatically-controlled cooling fan. The SEC-1235M has analog voltage and current meters on the front panel and is their only desktop model that has meters. Because of the possibility of meters, the illuminated power switch is on the front right corner above the internal cooling fan. Click here for an inside photo of an SEC-1235M (courtesy of Phil AD5X). The DC output terminals are closer together and closer to the side of the unit than they are on the SEC-1212 or SEC-1223 supplies.
	SEC-12xxP Power Supply Manual 1.3 MB PDF file by Samlex The SEC-12xxP models are newer versions of the SEC-12xx supplies. They have the same ratings as the SEC-12xx supplies however they will automatically handle 120 or 240VAC input power; no internal jumper change required. The SEC-1235PM has a dual back-lit meter and an illumination on/off switch. The fan, for those supplies that have one, has been relocated to the rear panel of the supply. This manual actually covers all of the SEC-12xxP series switching power supplies.
	Samlex desktop switching power supplies have two adjustment pots inside. The one that is closest to the rear of the chassis is labeled VR2 and it adjusts the output voltage. The one that is more centrally located and easier to get to is labeled VR1 and it sets the maximum output current. Most desktop switching power supplies do not have an over-voltage crowbar circuit and neither do the Samlex units, therefore the output voltage can easily be adjusted to 12-16VDC.
	Samlex desktop switching power supplies will go into current limiting a few amps above their rated maximum current. When this occurs, the voltage drops down to just a couple of volts but the current remains at the maximum value; it does not fold back as happens in Astron and most other linear power supplies.
	A number of the Samlex desktop switching power supplies use odd DC output terminals that fit into 1/2 inch square holes in the rear of the chassis. They accept 5mm round terminal pins. Stranded wires should be twisted and tinned to become a solid wire or crimped into an appropriate terminal pin. They use a 5/64 hex socket set screw that is #10, 24 TPI, 5/16 inch long. A hex key (Allen wrench) is supplied with the power supply. Older supplies used a slotted brass set screw that was easily broken. An M4x0.7 screw also fits.
	Samlex desktop switching power supplies produced for 120VAC mains voltage have an internal line fuse with the following ratings: SEC-1212: 5mm x 20mm Glass Fuse, 250V, 3.0A, Time Delay Type, LittelFuse 239003 SEC-1223: 5mm x 20mm Glass Fuse, 250V, 6.3A, Time Delay Type, LittelFuse 21806.3 SEC-1235: 5mm x 20mm Glass Fuse, 250V, 8.0A, Time Delay Type, LittelFuse 218008 When purchasing these fuses, they often have a "TnA" part number, where "T" stands for "Time Delay" (also known as Slo-Blo) and "n" is the current in amps. See the manual for 240VAC mains fuse ratings.
	Eric Lemmon WB6FLY (SK) performed load tests of the Samlex SEC-1212 and the Yaesu FP-1023 (a Samlex SEC-1223 inside) that can be found in the "AC and DC Power-Related Information" section of the Technical Information page of this website.
	There is about an inch of room behind the front panel to install a small LED or LCD meter and selector switch, but the metal is pretty thick and it may not be easy to cut a square hole to insert the meter through. See the inside photos above. It might be easier to install an external voltmeter and ammeter, or just buy a supply with meters, such as the SEC-1235M.
	Samlex offers a rack mount chassis to hold their desktop switching power supplies. See their web page for further details and models.

	SEC-100BRM 13.8 volt 100 amp Rack-Mount Power Supply 910 kB PDF file SEC-100BRM 13.8 volt 100 amp Rack-Mount Power Supply Specification Sheet 327 kB PDF file This is the manual for the above 40, 60, 80, and 100 amp rack mount power supplies. Internally they use from two to five 20-amp modules that are in parallel (marketed as "N+1 redundancy"). A lower amperage unit can be field upgraded by field installing additional SEC-2012MPSB modules (at the time of this update they were about US$80 to $100 each). This unit has a front panel voltmeter / ammeter, a fan failure LED, and five green LEDs showing the functionality of the internal 20-amp SEC-2012MPSB modules (from two to five) that are in parallel (marketed as "N+1 redundancy"). There is a 25 pin D-sub female connector on the rear for remote monitoring of the DC voltage output, the DC current drawn, the output of each of the five 20-amp modules, failure of either of the two DC fans, the presence of AC mains power, and more. The pinout of that connector is here (it's just one page from the manual). There is no single output that indicates a module failure but you can create one by diode-ORing the individual module fail pins.. Note that this model is NOT modifiable for 240 volt AC input, Samlex makes the SEC-100BRM-230 model for that. They also make other models with 24 volt output. Your page maintainer has about a dozen of the 12 volt 100 amp supplies in commercial mountaintop service, one site has five supplies. I've always ordered a 100 amp unit, the last few times I've received a 40 amp unit (two modules) and the other three modules in their own wrapping (I've had to assemble them). There are four high current connections on the rear, two for the DC output and two for a backup battery. The two ground terminals are paralleled inside. Internally there is a battery charger feature that can be easily disabled if the site backup battery has its own charger... however it is NOT a multistage charger, it is a simple constant-voltage trickle charger (8 amps maximum of charging current) using a 0.39 ohm power resistor (actually two 0.78 ohm resistors in parallel) between the power supply positive output terminal and the battery positive terminal. Depending on the output voltage of the supply and the type of battery it could overcharge or undercharge your battery, and in case of a extended power failure the 8 amp (maximum) trickle charger could take a very, very, very long time to recharge your site battery. Your page maintainer uses the SEC-series power supplies with the internal charger disabled. The battery charging function at our sites is provided by one or two of the SEC-1250UL (50 amps) or SEC-1235UL (35 amps) battery chargers - each site has between 400 and 800 amp-hours of backup battery.
	SEC-1230UL 13.8 volt 30 amp Multistage battery Charger Spec Sheet 481 KB PDF file This is the specification sheet for the yellow Samlex 30 amp multistage battery charger.
	SEC-1215UL (15 amp) and SEC-1230UL (30 amp) 13.8 volt Multistage battery Charger Manual 2.2 MB PDF file This is the manual for the yellow Samlex 15 and 30 amp multistage battery chargers. Your page maintainer has a few of the 30 amp units at mountaintop sites.
	SEC-1250UL 13.8 volt 50 amp Multistage battery Charger Spec Sheet 447 KB PDF file This is the specification sheet for the yellow Samlex 50 amp multistage battery chargers.
	SEC-1250UL 13.8 volt 50 amp Multistage battery Charger Manual 2.3 MB PDF file This is the manual for the yellow Samlex 50 amp multistage battery chargers. Your page maintainer has a number of these 50 amp units at mountaintop sites. One trick tp tell them apart: The 30 amp charger has one meter, the 50 amp model has two.
	SEC-1223 120V to 240V Modification 750 kB PDF file The other supplies can be similarly modified; the procedure is described in the manuals above. The yellow jumper wire can easily be seen in the two photos above, between the two large filter capacitors. The newest SEC-12xxP models automatically detect and handle either 120V or 240V input voltages, so no jumper is present in these units.
	SEC-1223 RF Filter Modification 720 KB PDF file by Nigel ZL2DF
	KA7500B Switching Mode Regulator IC Datasheet 61 KB PDF file Many Samlex desktop switching power supplies use this IC.
	TL494 Switching Mode Regulator IC Datasheet 1.3 MB PDF file This is functionally equivalent to the KA7500B above and is a very common IC in desktop switching power supplies made by Astron and other companies.
	Samlex SEC-1223 Modifications 1.8 MB PDF file While listed for the SEC-1223, this also pertains to the SEC-1212, SEC-1235, and SEC-1235M power supplies. The yellow 120V/240V jumper is similar in the other models but the pins are labeled with different letters. It also contains an unofficial schematic and parts list. Some of this information is available separately above.
	Samlex SEC-1223 Power Supply Repair 1.0 MB PDF file A repair article by Paul Robertson N2XZF.